#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <ctype.h>
using namespace std;
const int basesize = 1024;
const int argvnum = 64;
const int envnum = 64;
// 全局的命令⾏参数表
char* gargv[argvnum];
int gargc = 0;
// 全局的变量
int lastcode = 0;
// 我的系统的环境变量
char* genv[envnum];
// 全局的当前shell⼯作路径
char pwd[basesize];
char pwdenv[basesize];
// 全局变量与重定向有关
#define NoneRedir 0
#define InputRedir 1
#define OutputRedir 2
#define AppRedir 3
int redir = NoneRedir;
char* filename = nullptr;
// " "file.txt
#define TrimSpace(pos) do{\
while(isspace(*pos)){\
pos++;\
}\
}while(0)
string GetUserName()
{
	string name = getenv("USER");
	return name.empty() ? "None" : name;
}
string GetHostName()
{
	string hostname = getenv("HOSTNAME");
	return hostname.empty() ? "None" : hostname;
}
string GetPwd()
{
	if (nullptr == getcwd(pwd, sizeof(pwd))) return "None";
	snprintf(pwdenv, sizeof(pwdenv), "PWD=%s", pwd);
	putenv(pwdenv); // PWD=XXX
	return pwd;
	//string pwd = getenv("PWD");
	//return pwd.empty() ? "None" : pwd;
}
string LastDir()
{
	string curr = GetPwd();
	if (curr == "/" || curr == "None") return curr;
	// /home/whb/XXX
	size_t pos = curr.rfind("/");
	if (pos == std::string::npos) return curr;
	return curr.substr(pos + 1);
}
string MakeCommandLine()
{
	// [whb@bite-alicloud myshell]$
	char command_line[basesize];
	snprintf(command_line, basesize, "[%s@%s %s]# ", \
		GetUserName().c_str(), GetHostName().c_str(), LastDir().c_str());
	return command_line;
}
void PrintCommandLine() // 1. 命令⾏提⽰符
{
	printf("%s", MakeCommandLine().c_str());
	fflush(stdout);
}
bool GetCommandLine(char command_buffer[], int size) // 2. 获取⽤⼾命令
{
	// 我们认为：我们要将⽤⼾输⼊的命令⾏，当做⼀个完整的字符串
	// "ls -a -l -n"
	char* result = fgets(command_buffer, size, stdin);
	if (!result)
	{
		return false;
	}
	command_buffer[strlen(command_buffer) - 1] = 0;
	if (strlen(command_buffer) == 0) return false;
	return true;
}
void ResetCommandline()
{
	memset(gargv, 0, sizeof(gargv));
	gargc = 0;
	// 重定向
	redir = NoneRedir;
	filename = nullptr;
}
void ParseRedir(char command_buffer[], int len)
{
	int end = len - 1;
	while (end >= 0)
	{
		if (command_buffer[end] == '<')
		{
			redir = InputRedir;
			command_buffer[end] = 0;
			filename = &command_buffer[end] + 1;
			TrimSpace(filename);
			break;
		}
		else if (command_buffer[end] == '>')
		{
			if (command_buffer[end - 1] == '>')
			{
				redir = AppRedir;
				command_buffer[end] = 0;
				command_buffer[end - 1] = 0;
				filename = &command_buffer[end] + 1;
				TrimSpace(filename);
				break;
			}
			else
			{
				redir = OutputRedir;
				command_buffer[end] = 0;
				filename = &command_buffer[end] + 1;
				TrimSpace(filename);
				break;
			}
		}
		else
		{
			end--;
		}
	}
}
void ParseCommand(char command_buffer[])
{
	// "ls -a -l -n"
	const char* sep = " ";
	gargv[gargc++] = strtok(command_buffer, sep);
	// =是刻意写的
	while ((bool)(gargv[gargc++] = strtok(nullptr, sep)));
	gargc--;
}
void ParseCommandLine(char command_buffer[], int len) // 3. 分析命令
{
	ResetCommandline();
	ParseRedir(command_buffer, len);
	ParseCommand(command_buffer);
	//printf("command start: %s\n", command_buffer);
	// "ls -a -l -n"
	// "ls -a -l -n" > file.txt
	// "ls -a -l -n" < file.txt
	// "ls -a -l -n" >> file.txt
	//printf("redir: %d\n", redir);
	//printf("filename: %s\n", filename);
	//printf("command end: %s\n", command_buffer);
}
void debug()
{
	printf("argc: %d\n", gargc);
	for (int i = 0; gargv[i]; i++)
	{
		printf("argv[%d]: %s\n", i, gargv[i]);
	}
}
//enum
//{
// FILE_NOT_EXISTS = 1,
// OPEN_FILE_ERROR,
//};
void DoRedir()
{
	// 1. 重定向应该让⼦进程⾃⼰做！
	// 2. 程序替换会不会影响重定向?不会
	// 0. 先判断 && 重定向
	if (redir == InputRedir)
	{
		if (filename)
		{
			int fd = open(filename, O_RDONLY);
			if (fd < 0)
			{
				exit(2);
			}
			dup2(fd, 0);
		}
		else
		{
			exit(1);
		}
	}
	else if (redir == OutputRedir)
	{
		if (filename)
		{
			int fd = open(filename, O_CREAT | O_WRONLY | O_TRUNC, 0666);
			if (fd < 0)
			{
				exit(4);
			}
			dup2(fd, 1);
		}
		else
		{
			exit(3);
		}
	}
	else if (redir == AppRedir)
	{
		if (filename)
		{
			int fd = open(filename, O_CREAT | O_WRONLY | O_APPEND, 0666);
			if (fd < 0)
			{
				exit(6);
			}
			dup2(fd, 1);
		}
		else
		{
			exit(5);
		}
	}
	else
	{
		// 没有重定向,Do Nothong!
	}
}
// 在shell中
// 有些命令，必须由⼦进程来执⾏
// 有些命令，不能由⼦进程执⾏，要由shell⾃⼰执⾏ --- 内建命令 built command
bool ExecuteCommand() // 4. 执⾏命令
{
	// 让⼦进程进⾏执⾏
	pid_t id = fork();
	if (id < 0) return false;
	if (id == 0)
	{
		//⼦进程
		DoRedir();
		// 1. 执⾏命令
		execvpe(gargv[0], gargv, genv);
		// 2. 退出
		exit(7);
	}
	int status = 0;
	pid_t rid = waitpid(id, &status, 0);
	if (rid > 0)
	{
		if (WIFEXITED(status))
		{
			lastcode = WEXITSTATUS(status);
		}
		else
		{
			lastcode = 100;
		}
		return true;
	}
	return false;
}
void AddEnv(const char* item)
{
	int index = 0;
	while (genv[index])
	{
		index++;
	}
	genv[index] = (char*)malloc(strlen(item) + 1);
	strncpy(genv[index], item, strlen(item) + 1)
		genv[++index] = nullptr;
}
// shell⾃⼰执⾏命令，本质是shell调⽤⾃⼰的函数
bool CheckAndExecBuiltCommand()
{
	if (strcmp(gargv[0], "cd") == 0)
	{
		// 内建命令
		if (gargc == 2)
		{
			chdir(gargv[1]);
			lastcode = 0;
		}
		else
		{
			lastcode = 1;
		}
		return true;
	}
	else if (strcmp(gargv[0], "export") == 0)
	{
		// export也是内建命令
		if (gargc == 2)
		{
			AddEnv(gargv[1]);
			lastcode = 0;
		}
		else
		{
			lastcode = 2;
		}
		return true;
	}
	else if (strcmp(gargv[0], "env") == 0)
	{
		for (int i = 0; genv[i]; i++)
		{
			printf("%s\n", genv[i]);
		}
		lastcode = 0;
		return true;
	}
	else if (strcmp(gargv[0], "echo") == 0)
	{
		if (gargc == 2)
		{
			// echo 
			// echo $PATH
// echo hello
			if (gargv[1][0] == '$')
			{
				if (gargv[1][1] == '?')
				{
					printf("%d\n", lastcode);
					lastcode = 0;
				}
			}
			else
			{
				printf("%s\n", gargv[1]);
				lastcode = 0;
			}
		}
		else
		{
			lastcode = 3;
		}
		return true;
	}
	return false;
}
// 作为⼀个shell，获取环境变量应该从系统的配置来
// 我们今天就直接从⽗shell中获取环境变量
void InitEnv()
{
	extern char** environ;
	int index = 0;
	while (environ[index])
	{
		genv[index] = (char*)malloc(strlen(environ[index]) + 1);
		strncpy(genv[index], environ[index], strlen(environ[index]) + 1);
		index++;
	}
	genv[index] = nullptr;
}

